2013
DOI: 10.1073/pnas.1315053111
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Rationale and mechanism for the low photoinactivation rate of bacteria in plasma

Abstract: The rate of bacterial photoinactivation in plasma by methylene blue (MB), especially for Gram-negative bacteria, has been reported to be lower, by about an order of magnitude, than the rate of inactivation in PBS and water solutions. This low inactivation rate we attribute to the bleaching of the 660-nm absorption band of MB in plasma that results in low yields of MB triplet states and consequently low singlet oxygen generation. We have recorded the change of the MB 660-nm-band optical density in plasma, album… Show more

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Cited by 24 publications
(9 citation statements)
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“…These time resolved spectra changes indicate that while the 660 nm MB band OD decreases with light exposure at a rather high rate, the intensity of the 400 nm ADPA absorption band remains constant. These data are in agreement with the previously published data 24 that attribute the bleaching of the MB excited state to the loss of the MB ring conjugation, possibly, by the addition of an H-atom to the MB central ring nitrogen atom, forming the leuco-MB type molecule which does not absorb at 660 nm, Scheme 1. The expected very low photogeneration of singlet oxygen, if any, in the plasma/MB solu-Scheme 2 tions is substantiated by the unaltered OD of the 400 nm absorption band of ADPA with illumination, Fig.…”
Section: Relationship Between Bleaching Mb and Singlet Oxygen Generationsupporting
confidence: 93%
See 1 more Smart Citation
“…These time resolved spectra changes indicate that while the 660 nm MB band OD decreases with light exposure at a rather high rate, the intensity of the 400 nm ADPA absorption band remains constant. These data are in agreement with the previously published data 24 that attribute the bleaching of the MB excited state to the loss of the MB ring conjugation, possibly, by the addition of an H-atom to the MB central ring nitrogen atom, forming the leuco-MB type molecule which does not absorb at 660 nm, Scheme 1. The expected very low photogeneration of singlet oxygen, if any, in the plasma/MB solu-Scheme 2 tions is substantiated by the unaltered OD of the 400 nm absorption band of ADPA with illumination, Fig.…”
Section: Relationship Between Bleaching Mb and Singlet Oxygen Generationsupporting
confidence: 93%
“…The relative amount of singlet oxygen generated by each MB solution, after 661 nm LED illumination was determined by the slope of the decay of the 400 nm ADPA band OD as a function of irradiation time. 23 ADPA is known to react with singlet oxygen, to form endoperoxide, ADPA-O 2 , which does not absorb in the 400 nm region where ADPA has its first excited singlet state absorption band, 23,24 Scheme 2. Therefore the decrease of the 400 nm ADPA absorption band is a measure of the amount of singlet oxygen formed.…”
Section: Relationship Between Bleaching Mb and Singlet Oxygen Generationmentioning
confidence: 99%
“…Bacterial inactivation has recently received much attention due to the rising concern of antibiotic resistance 1 . Many alternative bacterial inactivation techniques have been developed, including the promising light-induced photo-inactivation methods such as photodynamic 2 6 and photothermal 7 11 treatments. The former relies on the interaction of light at frequencies typically in the visible and near-infrared range with photosensitizers which produce reactive species.…”
Section: Introductionmentioning
confidence: 99%
“…10 μM AMDA was added to the solutions containing monomicrobial and polymicrobial S. aureus and P. aeruginosa (10 8 CFU/mL) biofilms in PBS followed by the treatment as explained above. The reduction in the 399-nm absorption peak of AMDA after treatment corresponds to the amount of singlet oxygen produced 68 .O.D in untreated group (control) was taken as 100%. …”
Section: Methodsmentioning
confidence: 99%